Optimal dynamic spectrum access algorithm in bidirectional cognitive relay networks

In this paper, we study the optimal spectrum access in cognitive relay networks where multiple secondary users can access the unutilized idle spectrum of the primary users and conduct bidirectional communication. The spectrum access problem in the considered system model is defined as joint relay selection and discrete power control. Our goal is to maximize network utility function which takes the sum rate and the power consumption into account. We propose a decentralized synchronous update algorithm to obtain the optimal solution rather than the high complicated exhaustive search algorithm. In our proposed algorithm, we design a new objective function which consists of the network utility function and the penalty functions. Our designed objective function can guarantee the feasibility of the solution without knowing the infeasible strategy profiles in advance under mild conditions. It is proved that our proposed algorithm can converge to the optimal solution in finite steps. Simulation results verify our theoretic analysis.